1. Field of the Invention
The invention relates generally to apparatus for deploying a sign. More particularly, the invention relates to an apparatus for electromechanically deploying a school bus stop sign.
2. Description of the Prior Art
Since the 1930's, school buses have been equipped with a stop sign mechanism powered by a vacuum system. The sign is normally held against the side of the bus by a spring retainer. When the control valve is opened, the vacuum pulls in a diaphragm which overrides the spring retainer and causes the sign to swing out about a vertical axis. Appropriate circuitry is connected to a vacuum valve plunger to activate blinking lights on the sign and on the front and back of the bus. However, the sign itself is deployed solely by the vacuum system. Closing of the valve causes the diaphragm to return to its normal position and the sign returns to the side of the bus.
Use of the vacuum system necessitates the location of a large vacuum source tank on the chassis of the bus and running of tubing from a vacuum source (the engine intake manifold) to the tank, through a valve and to the diaphragm. Such tubing, especially when made from copper, is expensive to purchase and even more expensive to install. A rupture of any of the tubing renders the sign system inoperative. The neoprene diaphragm of the vacuum system can develop air leaks from being exposed to the weather. It is a time consuming repair job (up to 11/2 hours) to remove the sign from the bus, disassemble it, replace the diaphragm, reassemble and replace the sign. U.S. Pat. No. 2,252,529 describes this vacuum sign.
U.S. Pat. Nos. 2,144,813; 2,243,472 and 2,281,717 are illustrative of attempts at providing efficient electro-mechanical motor vehicle signal devices. German Patent 682897 also shows an electromechanical sign device.
U.S. Pat. Nos. 2,384,689 and 3,094,683 are illustrative of manually-operated school bus sign devices.
It is believed that no one has ever developed an acceptable electromechanically driven swing-out sign for school buses. The sole manufacturer of swing-out signs for school buses has not deemed it necessary to introduce any of the electrically-driven models developed. Lack of communication of any of the patented electrical-driven signs indicates that they were unacceptable in the market or for commercialization. However, with approximately 50,000 school buses being sold in the United States each year, there is an acute need for a reliable and easy-to-maintain electrical sign which will eliminate the vacuum tank and accompanying tubing.